Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of metered mail king Pitney Bowes (NYSE:PBI) sank 14% today after its quarterly results and guidance disappointed Wall Street.

So what: The company's weak third-quarter results -- earnings fell to $76.5 million from $172.8 million in the year-ago period while revenue declined 6.5% -- coupled with downbeat guidance for the full year reinforces concerns over its growth opportunities going forward. Management blamed the weak global economy for the miss, but the persistent trend away from traditional mail toward cheaper and faster forms of communication (email, fax, etc.) is what really concerns Wall Street about the business model.

Now what: Management now sees full-year EPS from continuing operations of $1.95 to $2.15, down significantly from a prior view of $2.12 to $2.32. "We continue to take actions to drive sustainable long-term growth for Pitney Bowes and our shareholders," Chairman and CEO Murray Martin reassuredinvestors. "As we focus on the higher growth opportunities, we are growing our participation in e-commerce opportunities related to cross border parcel shipping services." Given just how rapidly the market landscape is shifting, however, I'd remain cautious about buying into that optimism.

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This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.